Photomasks for reducing thermal stress generated by heat

ABSTRACT

A photomask includes a light transmission substrate having a transfer region and a frame region, a light-transmitting region exposing a portion of the light transmission substrate in the transfer region corresponding to a transfer pattern, a phase shift region surrounding the light-transmitting region in the transfer region. The phase shift region includes a first phase shift region surrounding the light-transmitting region and a second phase shift region surrounding the first phase shift region. A first phase shift pattern is disposed on the light transmission substrate in the first phase shift region, and a plurality of second phase shift patterns are disposed on the light transmission substrate in the second phase shift region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/742,394 filed on Jun. 17, 2015, entitled PHOTOMASKS FOR REDUCINGTHERMAL STRESS GENERATED BY HEAT, which claims priority under 35 U.S.C119(a) to Korean Application No. 10-2015-0025835, filed on Feb. 24,2015, in the Korean intellectual property Office, the disclosures ofwhich are incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

Various embodiments of the present disclosure relate to photomasks usedin lithography processes and, more particularly, to photomasks forreducing thermal stress generated by heat.

2. Related Art

In general, a semiconductor device may include a plurality of patternsdisposed over a semiconductor substrate. The patterns may be formedusing a photolithography process and an etch process to realize activeelements and/or passive elements. The photolithography process may beused to form photoresist patterns. More specifically, thephotolithography process may be performed by coating a photoresistmaterial on a target layer to form a photoresist layer, by selectivelyexposing portions of the photoresist layer to light with a photomask,and by developing the exposed photoresist layer to form the photoresistpatterns. The photoresist patterns may be used as etch masks forpatterning the target layer. As such, the photomask may be used totransfer predetermined patterns onto the photoresist layer and may begenerally comprised of a light transmission substrate and a plurality oftransfer patterns disposed on the light transmission substrate.

SUMMARY

Various embodiments are directed to photomasks for reducing thermalstress generated by heat.

According to an embodiment, a photomask includes a light transmissionsubstrate having a transfer region and a frame region, alight-transmitting region exposing a portion of the light transmissionsubstrate in the transfer region corresponding to a transfer pattern, aphase shift region surrounding the light-transmitting region in thetransfer region. The phase shift region includes a first phase shiftregion surrounding the light-transmitting region and a second phaseshift region surrounding the first phase shift region. A first phaseshift pattern is disposed on the light transmission substrate in thefirst phase shift region, and a plurality of second phase shift patternsare disposed on the light transmission substrate in the second phaseshift region.

According to an embodiment, a photomask includes a light transmissionsubstrate having a transfer region and a frame region, a transferpattern disposed on a portion of the light transmission substrate in thetransfer region, and a light-transmitting region surrounding thetransfer pattern in the transfer region. The light-transmitting regionincludes a first light-transmitting region surrounding the transferpattern and a second light-transmitting region surrounding the firstlight-transmitting region. The light transmission substrate in the firstlight-transmitting region is exposed. A plurality of light-blockingpatterns are disposed on the light transmission substrate in the secondlight-transmitting region. And each of the plurality of light-blockingpatterns has a closed loop shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure will become more apparentin view of the attached drawings and accompanying detailed description,in which:

FIG. 1 is a plan view illustrating a binary photomask according to anembodiment;

FIG. 2 is an enlarged view illustrating a portion of a transfer regionof the binary photomask shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along a line I-I′ of FIG. 2;

FIG. 4 is an enlarged view illustrating a portion of a frame region ofthe binary photomask shown in FIG. 1;

FIG. 5 is a cross-sectional view taken along a line II-II′ of FIG. 4;

FIG. 6 is a plan view illustrating a light-blocking region in a transferregion and a frame region included in the binary photomask shown in FIG.1 according to an embodiment;

FIG. 7 is a plan view illustrating a light-blocking region in a transferregion and a frame region included in the binary photomask shown in FIG.1 according to another embodiment;

FIG. 8 is a plan view illustrating a light-blocking region in a transferregion and a frame region included in the binary photomask shown in FIG.1 according to still another embodiment;

FIG. 9 is a plan view illustrating a phase shift photomask according toan embodiment;

FIG. 10 is an enlarged view illustrating a portion of a transfer regionof the phase shift photomask shown in FIG. 9;

FIG. 11 is a cross-sectional view taken along a line III-III′ of FIG.10;

FIG. 12 is an enlarged view illustrating a portion of a frame region ofthe phase shift photomask shown in FIG. 9;

FIG. 13 is a cross-sectional view taken along a line IV-IV′ of FIG. 12;

FIG. 14 is a plan view illustrating a phase shift region in a transferregion and a frame region included in the phase shift photomask shown inFIG. 9 according to an embodiment;

FIG. 15 is a plan view illustrating a phase shift region in a transferregion and a frame region included in the phase shift photomask shown inFIG. 9 according to another embodiment;

FIG. 16 is a plan view illustrating a phase shift region in a transferregion and a frame region included in the phase shift photomask shown inFIG. 9 according to still another embodiment;

FIG. 17 is a plan view illustrating a photomask according to anembodiment;

FIG. 18 is an enlarged view illustrating a portion of a transfer regionof the photomask shown in FIG. 17;

FIG. 19 is a cross-sectional view taken along a line V-V′ of FIG. 18;and

FIG. 20 is a schematic view illustrating an exposure system in which thephotomask of FIG. 17 is loaded.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In a photolithography process, light having a specific wavelength may beemitted from a light source and may irradiate a photoresist layer formedon a wafer through a photomask. Light-blocking regions of the photomaskmay prevent the light from irradiating the photoresist layer on thewafer, and only light-transmitting regions of the photomask may allowthe light to reach the wafer. The light-blocking regions may be regionson which light-blocking patterns are disposed. During thephotolithography process, the light-blocking patterns may absorb a largeamount of optical energy of the light irradiating the photomask, therebygenerating heat in the photomask. The heat may be conducted to a lighttransmission substrate of the photomask, and thus the light transmissionsubstrate may be expanded and deformed due to the heat. The thermaldeformation of the light transmission substrate may change positioncoordinates of patterns of the photomask, and thus cause an overlayerror between the photomask and the wafer in an exposure step.

In addition, the light penetrating the photomask may pass through aplurality of lenses constituting a lens module of an exposure system toreach the wafer. Thus, the plurality of lenses may also absorb theoptical energy of the light emitted from the light source to generateheat therein. As a result, the plurality of lenses may be expanded, andthus distort a phase of the light passing through the lenses. This maylead to an abnormal lithography process.

The following embodiments may provide photomasks which are capable ofsubstantially preventing the light emitted from the light source frombeing absorbed into transfer patterns such as light-blocking patterns orphase shift patterns of the photomasks during a photolithographyprocess. Moreover, the following embodiments may provide photomaskswhich may substantially prevent generation of thermal stress of lensesin an exposure system by reducing an amount of the light whichirradiates the lenses through light-transmitting regions of thephotomasks.

It will be understood that although the terms first, second, third, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another element. Thus, a first element in someembodiments could be termed a second element in other embodimentswithout departing from the teachings of the present disclosure.

It will also be understood that when an element is referred to as beinglocated “on”, “over”, “above”, “under”, “beneath” or “below” anotherelement, it may directly contact the other element, or at least oneintervening element may be present therebetween. Accordingly, the termssuch as “on”, “over”, “above”, “under”, “beneath”, “below” and the likethat are used herein are for the purpose of describing particularembodiments only and are not intended to limit the scope of the presentdisclosure.

It will be further understood that when an element is referred to asbeing “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent.

FIG. 1 is a plan view illustrating a binary photomask 100 according toan embodiment. In FIG. 1, a configuration for relieving thermal stressof the binary photomask 100 according to the present embodiment is notillustrated in order to reduce the complexity of the drawing. Theconfiguration for relieving the thermal stress of the binary photomask100 according to the present embodiment will be described in detail withreference to FIGS. 2 to 5. In addition, various configurations forrelieving thermal stress of photomasks according to other embodimentswill be described in detail with reference to FIGS. 6 to 8.

Referring to FIG. 1, the binary photomask 100 may have a transfer region110 and a frame region 120 surrounding the transfer region 110. Thetransfer region 110 may correspond to a region in which patternsconfigured to be transferred onto a wafer are disposed. The frame region120 may correspond to a marginal region which is provided to preventprocess errors that are due to double exposures between two adjacentshot areas defined in an exposure step. The two adjacent shot areas maybe two adjacent chip areas.

A plurality of transfer patterns 112 may be disposed in the transferregion 110. The plurality of transfer patterns 112 may betwo-dimensionally arrayed in rows and columns and spaced apart from eachother. In the present embodiment, the plurality of transfer patterns 112may have a uniform size and may be uniformly spaced apart from eachother. However, in some embodiments, sizes of the plurality of transferpatterns 112 may be nonuniform and/or distances between the plurality oftransfer patterns 112 may be nonuniform. In either embodiment, theconfiguration for relieving thermal stress of the binary photomask 100according to the present embodiment may be equally applicable.

As illustrated in FIG. 1, each of the transfer patterns 112 may be ahole-shaped pattern. However, the type of the transfer patterns 112illustrated in FIG. 1 is merely exemplary. For example, the transferpatterns 112 can be line patterns spaced apart from each other insteadof hole-shaped patterns. Although FIG. 1 illustrates the transferpatterns 112 each having a rectangular shape, embodiments are notlimited thereto. In some embodiments, the transfer patterns 112 may havenon-rectangular shapes. Each of the transfer patterns 112 may correspondto a light-transmitting region 114 which is comprised of a portion of alight transmission substrate exposed by an opening in a light-blockingregion 116. That is, the transfer region 110 may include thelight-transmitting regions 114 corresponding to the transfer patterns112 and the light-blocking region 116 surrounding the light-transmittingregions 114 in a plan view.

A configuration of the light-blocking region 116 will be described morefully with reference to FIGS. 2 and 3, which illustrate in detail aportion 150 of the transfer region 110 included in the binary photomask100. A light-blocking pattern such as a chromium (Cr) pattern may bedisposed in the frame region 120. Thus, the frame region 120 maysubstantially block light during an exposure step.

The transfer patterns 112 disposed in the transfer region 110 may betransferred onto a wafer by an exposure step. In particular, thetransfer patterns 112 corresponding to the light-transmitting regions114 may be transferred onto a positive tone resist layer formed on thewafer. Specifically, if an exposure step is performed with the binaryphotomask 100, portions of the positive tone resist layer thatcorrespond to the transfer patterns 112 may be exposed to light passingthrough the transfer patterns 112 disposed in the transfer region 110 ofthe binary photomask 100. Light may not irradiate the remaining portionof the positive tone resist layer that corresponds to the light-blockingregion 116 of the transfer region 110. As a result of the exposure step,a chemical structure of the exposed portions of the positive tone resistlayer may change. Thus, the exposed portions of the positive tone resistlayer may be selectively dissolved by a developer, and the transferpatterns 112 of the binary photomask 100 are transferred onto thepositive tone resist layer.

FIG. 2 is an enlarged view illustrating the portion 150 of the transferregion 110 of the binary photomask 100 shown in FIG. 1, and FIG. 3 is across-sectional view taken along a line I-I′ of FIG. 2. In FIGS. 2 and3, the same reference numerals as used in FIG. 1 denote the sameelements. Referring to FIGS. 1, 2 and 3, the transfer patterns 112 maycorrespond to the light-transmitting regions 114, which are comprised ofportions of a light transmission substrate 102 that are exposed in thetransfer region 110. The light-transmitting regions 114 may besurrounded by the light-blocking region 116.

A top surface 102 a of the light transmission substrate 102 in eachlight-transmitting region 114 may be exposed. Thus, during the exposurestep, the light irradiating a bottom surface 102 b of the lighttransmission substrate 102 may penetrate the light transmissionsubstrate 102 in the light-transmitting region 114 to reach a waferthrough the top surface 102 a of the light transmission substrate 102and a lens module (not shown) of an exposure system.

The light-blocking region 116 surrounding the light-transmitting regions114 may include a plurality of first light-blocking region 116 a and asecond light-blocking region 116 b. Each of the first light-blockingregions 116 a may have a uniform width W1 along a perimeter of acorresponding one of the light-transmitting regions 114 and surround thecorresponding light-transmitting region 114. In each of the firstlight-blocking regions 116 a, a first light-blocking pattern 117 may bedisposed on the top surface 102 a of the light transmission substrate102.

The second light-blocking region 116 b may correspond to a regionbetween the first light-blocking regions 116 a in the light-blockingregion 116. That is, the transfer region 110 may include thelight-transmitting regions 114 corresponding to the transfer patterns112, the first light-blocking regions 116 a surrounding thelight-transmitting regions 114, respectively, and the secondlight-blocking region 116 b disposed between the first light-blockingregions 116 a to surround the first light-blocking regions 116 a.

A plurality of second light-blocking patterns 118 may betwo-dimensionally arrayed along rows and columns in the secondlight-blocking region 116 b and spaced apart from each other in a planview. The top surface 102 a of the light transmission substrate 102 maybe partially exposed by the second light-blocking patterns 118. In thepresent embodiment, the exposed portion of the light transmissionsubstrate 102 between the second light blocking patterns 118 may be afirst exposure region 119-1. A distance D1 between the secondlight-blocking patterns 118 arrayed in each row may be substantiallyequal to a distance D2 between the second light-blocking patterns 118arrayed in each column.

Second light-blocking patterns 118′ may be second light-blockingpatterns 118 may include second light-blocking patterns 118′ disposeddirectly adjacent to each of the first light-blocking patterns 117. Theterm “directly adjacent” refers to a member of a group that is theclosest member of the group to another structure. A first structure thatis “directly adjacent” to a second structure does not necessarily touchthe second structure. A distance D3 between the first light-blockingpattern 117 and any one of the second light-blocking patterns 118′ maybe substantially equal to the distance D1 between the secondlight-blocking patterns 118 arrayed in each row and the distance D2between the second light-blocking patterns 118 arrayed in each column.The second light-blocking patterns 118 may be located at cross points ofthe rows and the columns. That is, the second light-blocking patterns118 may be two-dimensionally arrayed in a matrix form.

Each of the second light-blocking patterns 118 may have a rectangularclosed loop shape. That is, each of the second light-blocking patterns118 may have an opening that penetrates a central portion thereof.Accordingly, portions of the top surface 102 a of the light transmissionsubstrate 102 may be exposed by the openings of the secondlight-blocking patterns 118. In the present embodiment, the portions ofthe light transmission substrate 102 exposed by the openings of thesecond light-blocking patterns 118 may be second exposure regions 119-2.Thus, the light-blocking region 116 in the transfer region 110 mayinclude light-blocking regions covered with the first and secondlight-blocking patterns 117 and 118 and light-transmitting regionscomprised of the first and second exposure regions 119-1 and 119-2.

If the exposure step is performed with an exposure system in which thebinary photomask 100 is loaded, light 201 irradiating the bottom surface102 b of the light transmission substrate 102 may penetrate the lighttransmission substrate 102 and may exit out of the light transmissionsubstrate 102 through the top surface 102 a of the light transmissionsubstrate 102. The light 201 exiting out of the light transmissionsubstrate 102 may irradiate the positive tone resist layer formed on thewafer through the lens module of the exposure system. Since the light201 penetrating the light-transmitting regions 114 irradiates thepositive tone resist layer formed on the wafer, the transfer patterns112 may be transferred onto the positive tone resist layer. Most of thelight 201 irradiating the first and second light-blocking patterns 117and 118 in the light-blocking region 116 may be blocked from reachingthe positive tone resist layer formed on the wafer.

Meanwhile, the light 201 irradiating the first and second exposureregions 119-1 and 119-2 in the light-blocking region 116 may penetratethe light transmission substrate 102 and may exit out of the lighttransmission substrate 102 through the top surface 102 a of the lighttransmission substrate 102. However, in an embodiment, the first andsecond exposure regions 119-1 and 119-2 may have widths that arenarrower than a resolution limit of the exposure system. Thus, undesiredpatterns corresponding to the first and second exposure regions 119-1and 119-2 may not be transferred onto the positive tone resist layerformed on the wafer, and the light 201 exiting out of the first andsecond exposure regions 119-1 and 119-2 may not influence the transferof the transfer patterns 112 corresponding to the light-transmittingregions 114.

According to the above embodiment, an amount of the light absorbed intothe binary photomask 100 may be reduced by an amount of the lightpenetrating the light transmission substrate 102 in the first and secondexposure regions 119-1 and 119-2, as compared to a case in which anentire portion of the light-blocking region 116 is fully covered with alight-blocking layer. This may reduce thermal stress of the binaryphotomask 100 that is due to heat generated by the light absorbed intothe binary photomask 100 during the exposure step. As a result,deformation of the binary photomask 100 may be suppressed, thussubstantially preventing positions or shapes of the overlay patterns inthe binary photomask 100 from being changed.

FIG. 4 is an enlarged view illustrating a portion 160 of the frameregion 120 of the binary photomask 100 shown in FIG. 1, and FIG. 5 is across-sectional view taken along a line II-II′ of FIG. 4. In FIGS. 4 and5, the same reference numerals as used in FIG. 1 denote the sameelements. Referring to FIGS. 1, 4 and 5, a plurality of framelight-blocking patterns 128 may be two-dimensionally arrayed on the topsurface 102 a of the light transmission substrate 102 and spaced apartfrom each other. That is, the plurality of frame light-blocking patterns128 may be disposed in rows and columns in a plan view. The top surface102 a of the light transmission substrate 102 may be exposed between theframe light-blocking patterns 128. In the present embodiment, theexposed portion of the light transmission substrate 102 between theframe light blocking patterns 128 may be a first frame exposure region129-1.

A distance D4 between the frame light-blocking patterns 128 arrayed ineach row may be substantially equal to a distance D5 between the framelight-blocking patterns 128 arrayed in each column. These distances D4and D5 may be substantially equal to the distance D1 between the secondlight-blocking patterns 118 arrayed in each row and the distance D2between the second light-blocking patterns 118 arrayed in each columnwhich are described with reference to FIGS. 2 and 3. The framelight-blocking patterns 128 may be located at cross points of the rowsand the columns. That is, the frame light-blocking patterns 128 may betwo-dimensionally arrayed in a matrix form.

Each of the frame light-blocking patterns 128 may have a rectangularclosed loop shape. That is, each of the frame light-blocking patterns128 may have an opening that penetrates a central portion thereof.Accordingly, portions of the top surface 102 a of the light transmissionsubstrate 102 may be exposed by the openings of the frame light-blockingpatterns 128. In the present embodiment, the portions of the lighttransmission substrate 102 exposed by the openings of the framelight-blocking patterns 128 may be second frame exposure regions 129-2.Thus, the frame region 120 may include light-blocking regions coveredwith the frame light-blocking patterns 128 and light-transmittingregions comprised of the first and second frame exposure regions 129-1and 129-2.

If an exposure step is performed with the exposure system in which thebinary photomask 100 is loaded, most of light 202 irradiating the framelight-blocking patterns 128 in the frame region 120 may be blocked fromreaching the positive tone resist layer formed on the wafer. Meanwhile,the light 202 irradiating the first and second frame exposure regions129-1 and 129-2 in the frame region 120 may penetrate the lighttransmission substrate 102 and may exit out of the light transmissionsubstrate 102 through the top surface 102 a of the light transmissionsubstrate 102. The light 202 exiting out of the first and second frameexposure regions 129-1 and 129-2 may or may not irradiate the positivetone resist layer formed on the wafer.

For example, if the first and second frame exposure regions 129-1 and129-2 are designed to have widths that are narrower than a certainvalue, such that the light exiting out of the first and second frameexposure regions 129-1 and 129-2 has a low intensity, the light exitingout of the first and second frame exposure regions 129-1 and 129-2 doesnot change a chemical structure of the exposed portions of the positivetone resist layer. Accordingly, exposed portions of the positive toneresist layer may not be dissolved by a developer even though the light202 exiting out of the first and second frame exposure regions 129-1 and129-2 irradiates the positive tone resist layer. Alternatively, if thefirst and second frame exposure regions 129-1 and 129-2 may each have apredetermined width, such that the light exiting out of the first andsecond frame exposure regions 129-1 and 129-2 may be diffracted, thediffracted light may not irradiate the positive tone resist layer. Ineither case, undesired patterns corresponding to the first and secondexposure regions 129-1 and 129-2 may not be transferred onto thepositive tone resist layer formed on the wafer.

As compared with a case in which an entire portion of the frame region120 is fully covered with a light-blocking layer, in this embodiment, anamount of the light absorbed into the binary photomask 100 may bereduced by at least an amount of the light penetrating the lighttransmission substrate 102 in the first and second frame exposureregions 129-1 and 129-2. This may reduce thermal stress of the binaryphotomask 100 that is due to heat generated by the light absorbed intothe binary photomask 100. As a result, deformation of the binaryphotomask 100 may be suppressed, thus substantially preventing positionsor shapes of the overlay patterns in the binary photomask 100 from beingchanged. In particular, the overlay patterns are generally disposed inthe frame region. Thus, if the frame region 120 illustrated in FIGS. 4and 5 is employed in photomasks, an overlay accuracy may be improvedbecause deformation of the overlay patterns in the photomasks may besuppressed.

FIGS. 6, 7 and 8 are plan views illustrating the light-blocking region116 and the frame region 120 included in the binary photomask 100 shownin FIG. 1 according to various embodiments. As illustrated in FIG. 6,each of second light-blocking patterns 138 disposed in thelight-blocking region 116 and each of frame light-blocking patterns 148disposed in the frame region 120 may have a circular closed loop shape(i.e., an annular shape). That is, each of the second light-blockingpatterns 138 and the frame light-blocking patterns 148 may have anopening that penetrates a central portion thereof. Accordingly, portionsof the top surface (102 a of FIG. 3) of the light transmission substrate(102 of FIG. 3) may be exposed by the openings of the secondlight-blocking patterns 138 and the openings of the frame light-blockingpatterns 148. An exposed portion of the light transmission substrate 102between the second light-blocking patterns 138 may be a first exposureregion 139-1, and portions of the light transmission substrate 102exposed by the openings of the second light-blocking patterns 138 may besecond exposure regions 139-2. Similarly, an exposed portion of thelight transmission substrate 102 between the frame light-blockingpatterns 148 may be a first frame exposure region 149-1, and portions ofthe light transmission substrate 102 exposed by the openings of theframe light-blocking patterns 148 may be second frame exposure regions149-2.

As illustrated in FIG. 7, each of second light-blocking patterns 158disposed in the light-blocking region 116 and each of framelight-blocking patterns 168 disposed in the frame region 120 may have arectangular shape. An exposed portion of the light transmissionsubstrate 102 between the second light-blocking patterns 158 may be afirst exposure region 159, and an exposed portion of the lighttransmission substrate 102 between the frame light-blocking patterns 168may be a first frame exposure region 169.

As illustrated in FIG. 8, each of second light-blocking patterns 178disposed in the light-blocking region 116 and each of framelight-blocking patterns 188 disposed in the frame region 120 may have acircular shape. In order to minimize a planar area of a space betweenthe second light-blocking patterns 178, the second light-blockingpatterns 178 may be arrayed on the first surface 102 a of the lighttransmission substrate 102 such that each of the second light-blockingpatterns 178 is disposed in a space surrounded by six of the secondlight-blocking patterns 178. Similarly, the frame light-blockingpatterns 188 may be arrayed on the first surface 102 a of the lighttransmission substrate 102 such that each of the frame light-blockingpatterns 188 is disposed in a space surrounded by six of the framelight-blocking patterns 188. That is, the second light-blocking patterns178 and the frame light-blocking patterns 188 may be located at centralpoints and vertices of a plurality of hexagons constituting a honeycombstructure, as illustrated in FIG. 8. An exposed portion of the lighttransmission substrate 102 between the second light-blocking patterns178 may be a first exposure region 179, and another exposed portion ofthe light transmission substrate 102 between the frame light-blockingpatterns 188 may be a first frame exposure region 189. In someembodiments, each of the second light-blocking patterns 178 and theframe light-blocking patterns 188 may have a hexagonal shape. The secondlight-blocking patterns 178 and the frame light-blocking patterns 188having the hexagonal shape may be disposed in the same array structureas illustrated in FIG. 8.

FIG. 9 is a plan view illustrating a phase shift photomask 300 accordingto an embodiment. In FIG. 9, a configuration for relieving thermalstress of the phase shift photomask 300 according to the presentembodiment is not illustrated in order to reduce the complexity of thedrawing. The configuration for relieving the thermal stress of the phaseshift photomask 300 according to the present embodiment will bedescribed in detail with reference to FIGS. 10 to 13. In addition,various configurations for relieving thermal stress of photomasksaccording to other embodiments will be described in detail withreference to FIGS. 14 to 16.

Referring to FIG. 9, the phase shift photomask 300 may have a transferregion 310 and a frame region 320 surrounding the transfer region 310.The transfer region 310 may correspond to a region in which patternsconfigured to be transferred onto a wafer are disposed. The frame region320 may correspond to a marginal region which is provided to preventprocess errors that are due to double exposures between two adjacentshot areas (e.g., two adjacent chip areas) defined in an exposure step.A plurality of transfer patterns 312 may be disposed in the transferregion 310. The plurality of transfer patterns 312 may betwo-dimensionally arrayed in rows and columns and spaced apart from eachother. In the present embodiment, the plurality of transfer patterns 312may have a uniform size and may be uniformly spaced apart from eachother. However, in some embodiments, sizes of the plurality of transferpatterns 312 may be nonuniform and/or distances between the plurality oftransfer patterns 312 may be nonuniform. In either embodiment, theconfiguration for relieving the thermal stress of the phase shiftphotomask 300 according to the present embodiment may be equallyapplicable.

As illustrated in FIG. 9, each of the transfer patterns 312 may be ahole-shaped pattern. However, the type of the transfer patterns 312illustrated in FIG. 9 is merely exemplary. For example, the transferpatterns 312 can be line patterns spaced apart from each other insteadof hole-shaped patterns. Although FIG. 9 illustrates an example in whicheach of the transfer patterns 312 has a rectangular shape, embodimentsare not limited thereto. In some embodiments, the transfer patterns 312may have non-rectangular shapes. Each of the transfer patterns 312 maycorrespond to a light-transmitting region 314 which is comprised of aportion of a light transmission substrate exposed by an opening in aphase shift region 316. That is, the transfer region 310 may include thelight-transmitting regions 314 corresponding to the transfer patterns312 and the phase shift region 316 surrounding the light-transmittingregions 314 in a plan view. A configuration of the phase shift region316 will be described more fully with reference to FIGS. 10 and 11,which illustrate in detail a portion 350 of the transfer region 310included in the phase shift photomask 300. A light-blocking pattern suchas a chromium (Cr) pattern may be disposed in the frame region 320.Thus, the frame region 320 may substantially block light during anexposure step.

The transfer patterns 312 disposed in the transfer region 310 may betransferred onto a wafer by an exposure step. In particular, thetransfer patterns 312 corresponding to the light-transmitting regions314 may be transferred onto a positive tone resist layer formed on thewafer. Specifically, if the exposure step is performed with the phaseshift photomask 300, portions of the positive tone resist layer thatcorrespond to the transfer patterns 312 may be exposed to light passingthrough the transfer patterns 312 disposed in the transfer region 310 ofthe phase shift photomask 300. Light passing through the phase shiftregion 316 may have an intensity of about 5% to 8% of the intensity ofthe light passing through the transfer patterns 312, and the lightpassing through the phase shift region 316 may irradiate a portion ofthe positive tone resist layer that corresponds to the phase shiftregion 316. The light passing through the phase shift region 316 mayhave a phase difference of about 180 degrees, as compared with the lightpassing through the transfer patterns 312. As a result, only theportions of the positive tone resist layer that correspond to thetransfer patterns 312 may be chemically changed and may be selectivelydissolved by a developer.

FIG. 10 is an enlarged view illustrating a portion 350 of the transferregion 310 of the phase shift photomask 300 shown in FIG. 9, and FIG. 11is a cross-sectional view taken along a line III-III′ of FIG. 10. InFIGS. 10 and 11, the same reference numerals as used in FIG. 9 denotethe same elements. Referring to FIGS. 9, 10 and 11, the transferpatterns 312 may correspond to the light-transmitting regions 314, whichare comprised of portions of a light transmission substrate 302 that areexposed in the transfer region 310. The light-transmitting regions 314may be surrounded by the phase shift region 316. A top surface 302 a ofthe light transmission substrate 302 in each light-transmitting region314 may be exposed. Thus, during the exposure step, the lightirradiating a bottom surface 302 b of the light transmission substrate302 may penetrate the light transmission substrate 302 in thelight-transmitting region 314 to reach a wafer through the top surface302 a of the light transmission substrate 302 and a lens module of anexposure system.

The phase shift region 316 surrounding the light-transmitting regions314 may include a plurality of first phase shift regions 316 a and asecond phase shift region 316 b. Each of the first phase shift regions316 a may have a uniform width W4 along a perimeter of a correspondingone of the light-transmitting regions 314 and surround the correspondinglight-transmitting region 314. In each of the first phase shift regions316 a, a first phase shift pattern 317 may be disposed on the topsurface 302 a of the light transmission substrate 302. The second phaseshift region 316 b may correspond to a region between the first phaseshift regions 316 a in the phase shift region 316. That is, the transferregion 310 may include the light-transmitting regions 314 correspondingto the transfer patterns 312, the first phase shift regions 316 asurrounding the light-transmitting regions 314, and the second phaseshift region 316 b surrounding the first phase shift regions 316 a.

A plurality of second phase shift patterns 318 may be two-dimensionallyarrayed along rows and columns in the second phase shift region 316 band spaced apart from each other in a plan view. The top surface 302 aof the light transmission substrate 302 may be exposed between thesecond phase shift patterns 318. In the present embodiment, the exposedportion of the light transmission substrate 302 between the second phaseshift patterns 318 may be a first exposure region 319-1. A distance D6between the second phase shift patterns 318 arrayed in each row may besubstantially equal to a distance D7 between the second phase shiftpatterns 318 arrayed in each column. The second phase shift patterns 318may include second phase shift patterns 318′ disposed directly adjacentto each of the first phase shift patterns 317. A distance D8 between thefirst phase shift pattern 317 and any one of the second phase shiftpatterns 318′ may be substantially equal to the distance D6 between thesecond phase shift patterns 318 arrayed in each row and the distance D7between the second phase shift patterns 318 arrayed in each column. Thesecond phase shift patterns 318 may be located at cross points of therows and the columns. That is, the second phase shift patterns 318 maybe two-dimensionally arrayed in a matrix form.

Each of the second phase shift patterns 318 may have a rectangularclosed loop shape. That is, each of the second phase shift patterns 318may have an opening that penetrates a central portion thereof.Accordingly, portions of the top surface 302 a of the light transmissionsubstrate 302 may be exposed by the openings of the second phase shiftpatterns 318. In the present embodiment, the portions of the lighttransmission substrate 302 exposed by the openings of the second phaseshift patterns 318 may be second exposure regions 319-2. Thus, the phaseshift region 316 in the transfer region 310 may include light-blockingregions covered with the first and second phase shift patterns 317 and318 and light-transmitting regions comprised of the first and secondexposure regions 319-1 and 319-2.

If an exposure step is performed with an exposure system in which thephase shift photomask 300 is loaded, light 401 irradiating the bottomsurface 302 b of the light transmission substrate 302 may penetrate thelight transmission substrate 302 and may exit out of the lighttransmission substrate 302 through the top surface 302 a of the lighttransmission substrate 302. The light 401 exiting out of the lighttransmission substrate 302 may irradiate a positive tone resist layerformed on a wafer through a lens module of the exposure system. Sincethe light 401 penetrating the light-transmitting regions 314 irradiatesthe positive tone resist layer formed on the wafer, the transferpatterns 312 may be transferred onto the positive tone resist layer. Thelight passing through the first and second phase shift patterns 317 and318 may have an intensity of about 5% to 8% of the intensity of thelight passing through the transfer patterns 312, and the light passingthrough the first and second phase shift patterns 317 and 318 may have aphase difference of about 180 degrees, as compared with the lightpassing through the transfer patterns 312.

Meanwhile, most of the light 401 irradiating the first and secondexposure regions 319-1 and 319-2 in the phase shift region 316 maypenetrate the light transmission substrate 302 and may exit out of thelight transmission substrate 302 through the top surface 302 a of thelight transmission substrate 302. However, the first and second exposureregions 319-1 and 319-2 may have widths that are narrower than aresolution limit of the exposure system. Thus, undesired patternscorresponding to the first and second exposure regions 319-1 and 319-2may not be transferred to the positive tone resist layer formed on thewafer, and the light 401 exiting out of the first and second exposureregions 319-1 and 319-2 may not influence the transfer of the transferpatterns 312 corresponding to the light-transmitting regions 314.

According to the above embodiment, an amount of the light absorbed intothe phase shift photomask 300 may be reduced by at least an amount ofthe light penetrating the light transmission substrate 302 in the firstand second exposure regions 319-1 and 319-2, as compared to a case inwhich an entire portion of the phase shift region 316 is fully coveredwith a phase shift layer. This may reduce thermal stress of the phaseshift photomask 300 that is due to heat generated by the light absorbedinto the phase shift photomask 300 during an exposure step. As a result,deformation of the phase shift photomask 300 may be suppressed, thussubstantially preventing positions or shapes of overlay patterns in thephase shift photomask 300 from being changed.

FIG. 12 is an enlarged view illustrating a portion 360 of the frameregion 320 of the phase shift photomask 300 shown in FIG. 9, and FIG. 13is a cross-sectional view taken along a line IV-IV′ of FIG. 12. In FIGS.12 and 13, the same reference numerals as used in FIG. 9 denote the sameelements. Referring to FIGS. 9, 12 and 13, a plurality of framelight-blocking patterns 328 may be two-dimensionally arrayed on the topsurface 302 a of the light transmission substrate 302 and spaced apartfrom each other. That is, the plurality of frame light-blocking patterns328 may be disposed in rows and columns in a plan view. Each of theframe light-blocking patterns 328 may include a phase shift pattern328-1 and a light-blocking pattern 328-2 which are sequentially stackedon the top surface 302 a of the light transmission substrate 302. Thetop surface 302 a of the light transmission substrate 302 may be exposedbetween the frame light-blocking patterns 328. In the presentembodiment, the exposed portion of the light transmission substrate 302between the frame light blocking patterns 328 may be a first frameexposure region 329-1. A distance D9 between the frame light-blockingpatterns 328 arrayed in each row may be substantially equal to adistance D10 between the frame light-blocking patterns 328 arrayed ineach column. These distances D9 and D10 may be substantially equal tothe distance D6 between the second phase shift patterns 318 arrayed ineach row and the distance D7 between the second light-blocking patterns318 arrayed in each column which are described with reference to FIGS.10 and 11. The frame light-blocking patterns 328 may be located at crosspoints of the rows and the columns. That is, the frame light-blockingpatterns 328 may be two-dimensionally arrayed in a matrix form.

Each of the frame light-blocking patterns 328 may have a rectangularclosed loop shape. That is, each of the frame light-blocking patterns328 may have an opening that penetrates a central portion thereof.Accordingly, portions of the top surface 302 a of the light transmissionsubstrate 302 may be exposed by the openings of the frame light-blockingpatterns 328. In the present embodiment, the portions of the lighttransmission substrate 302 exposed by the openings of the framelight-blocking patterns 328 may be second frame exposure regions 329-2.Thus, the frame region 320 may include light-blocking regions coveredwith the frame light-blocking patterns 328 and light-transmittingregions comprised of the first and second frame exposure regions 329-1and 329-2.

If an exposure step is performed with the exposure system in which thephase shift photomask 300 is loaded, most of light 402 irradiating theframe light-blocking patterns 328 in the frame region 320 may be blockedfrom reaching the positive tone resist layer formed on the wafer.Meanwhile, the light 402 irradiating the first and second frame exposureregions 329-1 and 329-2 in the frame region 320 may penetrate the lighttransmission substrate 302 and may exit out of the light transmissionsubstrate 302 through the top surface 302 a of the light transmissionsubstrate 302. The light 402 exiting out of the first and second frameexposure regions 329-1 and 329-2 may or may not irradiate the positivetone resist layer formed on the wafer.

For example, if the first and second frame exposure regions 329-1 and329-2 are designed to have widths that are narrower than a certainvalue, such that the light exiting out of the first and second frameexposure regions 329-1 and 329-2 has a low intensity, the light exitingout of the first and second frame exposure regions 329-1 and 329-2 doesnot change a chemical structure of exposed portions of the positive toneresist layer. Accordingly, the exposed portions of the positive toneresist layer may not be dissolved by a developer even though the light402 exiting out of the first and second frame exposure regions 329-1 and329-2 irradiates the positive tone resist layer.

Alternatively, if the first and second frame exposure regions 329-1 and329-2 may have a predetermined width, so that the light exiting out ofthe first and second frame exposure regions 329-1 and 329-2 may bediffracted, the diffracted light may not irradiate the positive toneresist layer. In either embodiment, undesired patterns corresponding tothe first and second exposure regions 329-1 and 329-2 may not betransferred onto the positive tone resist layer formed on the wafer.

As compared to a case in which an entire portion of the frame region 320is fully covered with a light-blocking layer, in this embodiment, anamount of the light absorbed into the phase shift photomask 300 may bereduced by at least an amount of the light penetrating the lighttransmission substrate 302 in the first and second frame exposureregions 329-1 and 329-2. This may reduce thermal stress of the phaseshift photomask 300 that is due to heat generated by the light absorbedinto the phase shift photomask 300. As a result, deformation of thephase shift photomask 300 may be suppressed, thus substantiallypreventing positions or shapes of the overlay patterns in the phaseshift photomask 300 from being changed. In particular, the overlaypatterns are generally disposed in the frame region. Thus, if the frameregion 320 illustrated in FIGS. 12 and 13 is employed in photomasks, anoverlay accuracy may be improved because deformation of the overlaypatterns in the photomasks may be suppressed.

FIGS. 14, 15 and 16 are plan views illustrating the phase shift region316 and the frame region 320 included in the phase shift photomask 300shown in FIG. 9 according to various embodiments. As illustrated in FIG.14, each of second phase shift patterns 338 disposed in the phase shiftregion 316 and each of frame light-blocking patterns 348 disposed in theframe region 320 may have a circular closed loop shape (i.e., an annularshape). That is, each of the second phase shift patterns 338 and theframe light-blocking patterns 348 may have an opening that penetrates acentral portion thereof. Accordingly, portions of the top surface (302 aof FIG. 11) of the light transmission substrate (302 of FIG. 11) may beexposed by the openings of the second phase shift patterns 338 and theframe light-blocking patterns 348. An exposed portion of the lighttransmission substrate 302 between the second phase shift patterns 338may be a first exposure region 339-1, and portions of the lighttransmission substrate 302 exposed by the openings of the second phaseshift patterns 338 may be second exposure regions 339-2. Similarly, anexposed portion of the light transmission substrate 302 between theframe light-blocking patterns 348 may be a first frame exposure region349-1, and portions of the light transmission substrate 302 exposed bythe openings of the frame light-blocking patterns 348 may be secondframe exposure regions 349-2.

As illustrated in FIG. 15, each of second phase shift patterns 358disposed in the phase shift region 316 and each of frame light-blockingpatterns 368 disposed in the frame region 320 may have a rectangularshape. An exposed portion of the light transmission substrate 302between the second phase shift patterns 358 may be a first exposureregion 359, and an exposed portion of the light transmission substrate302 between the frame light-blocking patterns 368 may be a first frameexposure region 369.

As illustrated in FIG. 16, each of second phase shift patterns 378disposed in the phase shift region 316 and each of frame light-blockingpatterns 388 disposed in the frame region 320 may have a circular shape.In order to minimize a planar area of a space between the second phaseshift patterns 378, the second phase shift patterns 378 may be arrayedon the first surface 302 a of the light transmission substrate 302 suchthat each of the second phase shift patterns 378 is disposed in a spacesurrounded by six of the second phase shift patterns 378. Similarly, theframe light-blocking patterns 388 may be arrayed on the first surface302 a of the light transmission substrate 302 such that each of theframe light-blocking patterns 388 is disposed in a space surrounded bysix of the frame light-blocking patterns 388. That is, the second phaseshift patterns 378 and the frame light-blocking patterns 388 may belocated at central points and vertices of a plurality of hexagonsconstituting a honeycomb structure, as illustrated in FIG. 16. Anexposed portion of the light transmission substrate 302 between thesecond phase shift patterns 378 may be a first exposure region 379, andanother exposed portion of the light transmission substrate 302 betweenthe frame light-blocking patterns 388 may be a first frame exposureregion 389. In some embodiments, each of the second phase shift patterns378 and the frame light-blocking patterns 388 may have a hexagonalshape. The second phase shift patterns 378 and the frame light-blockingpatterns 388 having the hexagonal shape may be disposed in the samearray structure as illustrated in FIG. 16.

FIG. 17 is a plan view illustrating a photomask 500 according to anembodiment. In FIG. 17, a configuration of the photomask 500 forpreventing a lens (or lens module) of an exposure system from beingheated is not illustrated in order to reduce the complexity of thedrawing. The configuration of the photomask 500 for preventing the lens(or lens module) of the exposure system from being heated will bedescribed in detail with reference to FIGS. 18 and 19.

Referring to FIG. 17, the photomask 500 may have a transfer region 510and a frame region 520 surrounding the transfer region 510. The transferregion 510 may correspond to a region in which patterns configured to betransferred onto a wafer are disposed. The frame region 520 maycorrespond to a marginal region which is provided to prevent processerrors that are due to double exposures between two adjacent shot areas(e.g., two adjacent chip areas) defined in an exposure step. A pluralityof transfer patterns 514 may be disposed in the transfer region 510. Theplurality of transfer patterns 514 may be two-dimensionally arrayed inrows and columns and spaced apart from each other. In the presentembodiment, the plurality of transfer patterns 514 may have a uniformsize and may be uniformly spaced apart from each other. However, in someembodiments, sizes of the plurality of transfer patterns 514 may benonuniform and/or distances between the plurality of transfer patterns514 may be nonuniform. In either embodiment, the configuration of thephotomask 500 for preventing the lens (or lens module) of the exposuresystem from being heated may be equally applicable.

As illustrated in FIG. 17, each of the transfer patterns 514 may be ahole-shaped pattern. However, the type of the transfer patterns 514illustrated in FIG. 17 is merely exemplary. For example, the transferpatterns 514 can be line patterns spaced apart from each other insteadof hole-shaped patterns. Although FIG. 17 illustrates an embodiment inwhich each of the transfer patterns 514 has a rectangular shape,embodiments are not limited thereto. In some embodiments, the transferpatterns 514 may have non-rectangular shapes. Each of the transferpatterns 514 may correspond to a light-blocking pattern or a phase shiftpattern. That is, the transfer region 510 may include the transferpatterns 514 such as light-blocking patterns or phase shift patterns anda light-transmitting region 516 surrounding the transfer patterns 514.The light-transmitting region 516 will be described more fully withreference to FIGS. 18 and 19, which illustrate in detail a portion 550of the transfer region 510 included in the photomask 500. Alight-blocking pattern such as a chromium (Cr) pattern may be disposedin the frame region 520. Thus, the frame region 520 may substantiallyblock light during an exposure step.

The transfer patterns 514 disposed in the transfer region 510 may betransferred onto a wafer by an exposure step. In particular, thetransfer patterns 514 corresponding to light-blocking patterns or phaseshift patterns may be transferred onto a negative tone resist layerformed on the wafer. Specifically, if the exposure step is performedwith the photomask 500, no light irradiates portions of the negativetone resist layer that correspond to the transfer patterns 514. Incontrast, a portion of the negative tone resist layer, which correspondsto the light-transmitting region 516, may be exposed to light passingthrough the light-transmitting region 516. As a result of the exposurestep, the exposed portions of the negative tone resist layer may becross-linked and polymerized to have a chemical structure that is notdissolved by a developer. Thus, if the negative tone resist layer isdeveloped after the exposure step is performed, only the non-exposedportions of the negative tone resist layer that correspond to thetransfer patterns 514 may be selectively removed.

FIG. 18 is an enlarged view illustrating the portion 550 of the transferregion 510 of the photomask 500 shown in FIG. 17, and FIG. 19 is across-sectional view taken along a line V-V′ of FIG. 18. In FIGS. 18 and19, the same reference numerals as used in FIG. 17 denote the sameelements. Referring to FIGS. 17, 18 and 19, the transfer patterns 514may be disposed on a top surface 502 a of a light transmission substrate502 in the transfer region 510. The transfer patterns 514 may besurrounded by the light-transmitting region 516. The light-transmittingregion 516 may correspond to a region in which the top surface 502 a ofthe light transmission substrate 502 is exposed. Thus, during theexposure step, the light irradiating a bottom surface 502 b of the lighttransmission substrate 502 may penetrate the light transmissionsubstrate 502 in the light-transmitting region 516 to reach the waferthrough the top surface 502 a of the light transmission substrate 502and a lens module of an exposure system.

The light-transmitting region 516 surrounding the transfer patterns 514may include a first light-transmitting region 516 a and a secondlight-transmitting region 516 b. The first light-transmitting region 516a may have a uniform width W3 along a perimeter of the transfer pattern514 and surround the transfer pattern 514. In the firstlight-transmitting region 516 a, an entire portion of the top surface502 a of the light transmission substrate 502 may be fully exposed. Thesecond light-transmitting region 516 b may surround the firstlight-transmitting region 516 a. Thus, the transfer region 510 mayinclude the transfer patterns 514, the first light-transmitting regions516 a surrounding the transfer patterns 514, and the secondlight-transmitting regions 516 b surrounding the firstlight-transmitting regions 516 a.

A plurality of light-blocking patterns 518 may be two-dimensionallyarrayed along rows and columns in the second light-transmitting region516 b and spaced apart from each other in a plan view. The top surface502 a of the light transmission substrate 502 may be exposed between thelight-blocking patterns 518 in the second light-transmitting region 516b. A distance D11 between the light-blocking patterns 518 arrayed ineach row may be substantially equal to a distance D12 between thelight-blocking patterns 518 arrayed in each column. The light-blockingpatterns 518 may be spaced apart from the first light-transmittingregion 516 a by a distance D13, and the distance D13 may be less thanthe distance D11 between the light-blocking patterns 518 arrayed in eachrow and the distance D12 between the light-blocking patterns 518 arrayedin each column. In some embodiments, the distance D13 between the firstlight-transmitting region 516 a and the light-blocking patterns 518 maybe about half the distance D11 between the light-blocking patterns 518arrayed in each row or about half the distance D12 between thelight-blocking patterns 518 arrayed in each column. The light-blockingpatterns 518 may be two-dimensionally arrayed in the secondlight-transmitting region 516 b to have a matrix form in a plan view.

Each of the light-blocking patterns 518 may have a rectangular closedloop shape. That is, each of the light-blocking patterns 518 may have anopening that penetrates a central portion thereof. A width of each sideof the light-blocking patterns 518 may be narrower than a resolutionlimit of the exposure system. Thus, the light-blocking patterns 518 maynot be transferred onto the wafer. Portions of the top surface 502 a ofthe light transmission substrate 502 may be exposed by the openings ofthe light-blocking patterns 518. Thus, the light-transmitting region 516may include the plurality of first light-transmitting regions 516 a andthe second light-transmitting regions 516 b. The secondlight-transmitting region 516 b may include light-transmitting regionsexposed by the openings of the light-blocking patterns 518,light-blocking regions covered by the light-blocking patterns 518, and alight-transmitting region between the light-blocking patterns 518.

FIG. 20 is a schematic view illustrating an exposure system 600 in whichthe photomask 500 of FIG. 17 is loaded. Referring to FIG. 20, thephotomask 500 may have the transfer patterns 514 corresponding tolight-blocking patterns or phase shift patterns and thelight-transmitting region 516 surrounding the transfer patterns 514, asdescribed with reference to FIGS. 17, 18 and 19. The light-blockingpatterns 518 having a smaller size than a resolution limit of theexposure system 600 may be disposed in the light-transmitting region516. The photomask 500 having the aforementioned configuration may beloaded into the exposure system 600, and light 601 generated from alight source (not shown) may irradiate the photomask 500. The light 601irradiating the photomask 500 may pass through the photomask 500 or maybe blocked by the photomask 500 according to structures of patternsdisposed on the photomask 500. Light passing through the photomask 500may irradiate a lens 610 (or lens module) of the exposure system 600, asindicated by arrows 602. Light passing through the lens 610 may travelalong appropriate optical paths and may reach a negative tone resistlayer 622 formed on a wafer 620, as indicated by arrows 603. In general,this exposure step may be repeatedly performed to expose a plurality ofchip regions included in the wafer 620. Thus, the light may berepeatedly irradiating the lens 610 while the exposure step isrepeatedly performed to expose the plurality of chip regions included inthe wafer 620.

Since the negative tone resist layer 622 is used as a resist layer, thelight-transmitting region 516 of the photomask 500 may have a relativelylarge area. During a single exposure step, an amount of the lightirradiating the lens 610 may increase as compared with the embodimentsillustrated in FIGS. 1 to 16. As a result, thermal stress of the lens610 may occur when it is heated, and thus the lens 610 may be deformed.As a result, an aberration of the lens 610 may be changed to degrade thequality of pattern images transferred onto the wafer 620. However,according to the present embodiments, the plurality of light-blockingpatterns 518 each having a width smaller than the resolution limit ofthe exposure system 600 may be disposed in the light-transmitting region516. Thus, an amount of the light irradiating the lens 610 may bereduced without transfer of patterns corresponding to the plurality oflight-blocking patterns 518. Accordingly, the thermal stress of the lens610 may be alleviated.

The embodiments of the present disclosure have been disclosed above forillustrative purposes. Those of ordinary skill in the art willappreciate that various modifications, additions, and substitutions arepossible, without departing from the scope and spirit of the presentdisclosure as claimed below.

What is claimed is:
 1. A photomask comprising: a light transmissionsubstrate having a transfer region and a frame region; alight-transmitting region exposing a portion of the light transmissionsubstrate in the transfer region corresponding to a transfer pattern;and a phase shift region surrounding the light-transmitting region inthe transfer region, wherein the phase shift region includes a firstphase shift region surrounding the light-transmitting region and asecond phase shift region surrounding the first phase shift region, andwherein a first phase shift pattern is disposed on the lighttransmission substrate in the first phase shift region, and a pluralityof second phase shift patterns are disposed on the light transmissionsubstrate in the second phase shift region.
 2. The photomask of claim 1,wherein the first phase shift region has a uniform width along aperimeter of the light-transmitting region.
 3. The photomask of claim 1,wherein the second phase shift patterns are spaced apart andtwo-dimensionally arrayed in rows and columns in the second phase shiftregion and the light transmission substrate is exposed between thesecond phase shift patterns.
 4. The photomask of claim 3, wherein adistance between the second phase shift patterns arrayed in each row issubstantially equal to a distance between the second phase shiftpatterns arrayed in each column.
 5. The photomask of claim 4, wherein adistance between the first phase shift pattern and any one of the secondphase shift patterns directly adjacent to the first phase shift patternis substantially equal to the distance between the second phase shiftpatterns arrayed in each row or the distance between the second phaseshift patterns arrayed in each column.
 6. The photomask of claim 1,wherein each of the second phase shift patterns has a rectangular shape,and the second phase shift patterns are arrayed on the lighttransmission substrate in a matrix form.
 7. The photomask of claim 1,wherein each of the second phase shift patterns has a circular shape,and the second phase shift patterns are arrayed on the lighttransmission substrate such that one second phase shift pattern isdisposed in a space surrounded by six of the second phase shiftpatterns.
 8. The photomask of claim 1, wherein each of the second phaseshift patterns has a rectangular or circular closed loop shape includingan opening that penetrates a central portion of the second phase shiftpattern, the opening exposing a portion of the light transmissionsubstrate.
 9. The photomask of claim 1, wherein the frame region isconfigured to include a plurality of frame light-blocking patterns whichare spaced apart and arrayed in rows and columns on the lighttransmission substrate.
 10. The photomask of claim 9, wherein the lighttransmission substrate is exposed between the frame light-blockingpatterns, and a distance between the frame light-blocking patternsarrayed in each row is substantially equal to a distance between theframe light-blocking patterns arrayed in each column.
 11. The photomaskof claim 9, wherein each of the frame light-blocking patterns has arectangular shape, and the frame light-blocking patterns are arrayed onthe light transmission substrate in a matrix form.
 12. The photomask ofclaim 9, wherein each of the frame light-blocking patterns has acircular shape, and the frame light-blocking patterns are arrayed on thelight transmission substrate such that one frame light-blocking patternis disposed in a space surrounded by six of the frame light-blockingpatterns.
 13. The photomask of claim 9, wherein each of the framelight-blocking patterns has a rectangular or circular closed loop shapeincluding an opening that penetrates a central portion of the framelight-blocking pattern, the opening exposing a portion of the lighttransmission substrate.
 14. The photomask of claim 9, wherein each ofthe frame light-blocking patterns includes a phase shift pattern and alight-blocking pattern that are sequentially stacked on the lighttransmission substrate.
 15. A photomask comprising: a light transmissionsubstrate having a transfer region and a frame region; a transferpattern disposed on a portion of the light transmission substrate in thetransfer region; and a light-transmitting region surrounding thetransfer pattern in the transfer region, wherein the light-transmittingregion includes a first light-transmitting region surrounding thetransfer pattern and a second light-transmitting region surrounding thefirst light-transmitting region, wherein the light transmissionsubstrate in the first light-transmitting region is exposed, wherein aplurality of light-blocking patterns are disposed on the lighttransmission substrate in the second light-transmitting region, andwherein each of the plurality of light-blocking patterns has a closedloop shape.
 16. The photomask of claim 15, wherein the transfer patternis a light-blocking pattern or a phase shift pattern.
 17. The photomaskof claim 15, wherein the first light-transmitting region has a uniformwidth along a perimeter of the transfer pattern.
 18. The photomask ofclaim 15, wherein the light transmission substrate is exposed betweenthe light-blocking patterns, and a distance between the light-blockingpatterns arrayed in each row is substantially equal to a distancebetween the light-blocking patterns arrayed in each column.
 19. Thephotomask of claim 18, wherein a distance between the firstlight-transmitting region and any one of the light-blocking patternsdirectly adjacent to the first light-transmitting region is less thanthe distance between the light-blocking patterns arrayed in each row orthe distance between the light-blocking patterns arrayed in each column.20. The photomask of claim 18, wherein the distance between the firstlight-transmitting region and any one of the light-blocking patterns isabout half the distance between the light-blocking patterns arrayed ineach row or is about half the distance between the light-blockingpatterns arrayed in each column.
 21. The photomask of claim 15, whereineach of the light-blocking patterns has an opening that penetrates acentral portion of the light-blocking pattern, the opening exposing aportion of the light transmission substrate.